CTorrent

CTorrent is fast and light weight un*x command line BitTorrent client, which is why it is the only BitTorrent client (other than the Bram Cohen's reference Python implementation) I would use. It is just so much easier to ssh into your Linux server, start the download inside a screen, detach it, and 10 hours later ssh'ed back (over congested link) and re-attach to find out it has only gathered half the pieces. Can't imaging doing that with a GUI :)